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Kawai K4 Synthesizer

This page documents my fascination with this interesting and seemingly overlooked jewel from the same era as the Roland D-50 and Korg M1.

"The K4 from Kawai can be thought of as a warm and fuzzy digital synthesizer. A sample-based digital synth, its sounds are those typically weird industrial type sounds that can still be useful in lo-fi, big-beat and trip hop music styles. The sounds are 16-bit preset PCM samples of acoustic instruments. However, unlike its predecessor the K1, the K4 adds a welcomed digital filter section. This truly makes the K4 more flexible, fun and useful for today's filter tweaking music effects!"
Vintage Synth Explorer

While there are quite a few examples of the K4 on YouTube, this one in particular captures a lot of the warmth and breadth of this synth.

This track shows off what some clever programmging on the K4 can achieve: Soundbank Demo (Soundcloud)


User Manuals

Internal Components

The K4 uses an NEC 78KIII series microcontroller, a uPD78310. I've managed to source some datasheets and other documents from the web.

Understanding How It Works

I couldn't resist it. After a few weeks hacking away I now have a disassembler for the uPD78310. It is part of the dasmxx project. You will need to get hold of a ROM image, either from a ROM pulled from a K4, or the latest ROM image from Kawai (see below). If you do the latter, convert the Motorola S-REC files into plain binary (I use the srecord tool). Then you are ready to run the raw binary through dasm78k3 once you have a disassembler command file. My own is presented as a work-in-progress:

As I begin to explore the code, I also had to work out the memory layout. Most of it is conventional:

  • 0000-7FFF = ROM
  • 8000-BFFF = paged RAM/card/ROM
  • C000-DFFF = RAM
  • E000-FDFF = external hardware blocks (sound engine, DSP, etc)
  • FE00-FFFF = internal memory and registers

The paged memory block (8000-BFFF) is controlled by two I/O pins P35 and P34 (pin 5 and pin 4 of Port 3 respectively):

00RAM (16k)
10ROM (region 8000-BFFF)
11ROM (region C000-FFFF)


The service manual can be purchased from W D Greenhill. Although you may baulk at paying for something you can find online I can say that the copy from Greenhill is of a much higher quality than what I have found online so far.

It is still possible to download the latest revision 1.4 ROM images from Kawai:

They are in Motorola S19 format, and you'll need a blank EPROM and suitable programmer to burn a new ROM.


First and foremost, the factory reset patches are available from Kawai (click on the link, choose "K4 / K4r" and download the ZIP file, then play the k4.mid file after you've set your MIDI output to point to the K4).

Editors / Librarians



K4 servicing
Vintage Synth
K4 rocks!

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